N-Tron ESERV-M12T, User Manual

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Properties ESERV-M12T Modbus Gateway ESERV-M12T Modbus Gateway
21 ESERV-M12T (Rev. 1210)
MODBUS SERIAL RETRIES
This is the maximum number of times that the Modbus gateway will retry to send a Modbus message to a Modbus
client, before reporting a 0Bh exception if it is selected. This should be limited to between 0 and 5.
MODBUS ASCII
The Modbus ASCII message protocol is a human readable version of the Modbus message, and is one of the three
Modbus formats supported by the ESERV-M12T Modbus Gateway.
A major advantage of Modbus ASCII is it allows up to a 1 second gap between bytes. It uses a Longitudinal
Redundancy Check (LRC) checksum to verify message accuracy.
MODBUS MESSAGE BUFFERING
The ESERV-M12T has two Modbus serial buffers, one for each serial port. Each will buffer up to 32 Modbus
messages.
These buffers help ensure messages don’t get lost in a data traffic jam, and are part of what makes
Modbus such an outstandingly reliable serial protocol.
MODBUS MESSAGE TIMEOUT
Message timeout is supported by the ESERV-M12T. This is the maximum amount of time before a response to a
message is expected.
MODBUS RTU MESSAGE
The Modbus RTU message is broken into 4 different parts. The address field, the function code, this is copied
directly over from the Modbus TCP message, the data and the error check, a 16 bit cyclic redundancy check or CRC.
MODBUS SERIAL CONTROL
MESSAGE TIMEOUT
The message timeout is the maximum time the gateway allows for a response from the slave device. The default is
1000ms.